The synthesis of serum amyloid A (SAA) is profoundly altered in response to acute inflammation and malignancy; however, of the molecular mechanisms by which SAA gene expression is regulated are not completely understood. Although the biological function of SAA is still not known, studies have shown that prolonged elevation of SAA in plasma would lead to a pathological condition called secondary amyloidosis. This is the result of deposition of amyloid A fibrils in organs such as the liver, heart and kidney. This deposition interferes with normal organ function and in more serious cases, can lead to death. Interestingly, while amyloidosis has been reported in human, mouse and few other species, it has not been observed in rats. For these reasons, studies are aimed towards the understanding the structure and organization of the rat SAA genes as well as the molecular mechanisms by which SAA genes are regulated following inflammation. Specifically, we propose: 1. To identify, isolate, and sequence the multiple forms of rat SAA cDNAs. 2. To construct rat SAA-beta-galactosidase fusion protein for raising antibodies against these different rat SAA proteins. With these antibodies, the biosynthesis of SAA in rats will be examined. 3. To characterize the structure and organization of rat SAA genes as well as to elucidate the complete DNA sequence of these genes. 4. To establish in a tissue culture system in which the induction of SAA gene expression can be demonstrated in vitro. 5. To identify and characterize cis-acting regulatory sequences that confer inflammation and cell-specific transcription of SAA genes. These studies will offer new insight into the pathophysiology of amyloidosis and the biological importance of SAA to its host. In addition, studies on the structure and regulation of SAA genes will contribute to the understanding of the coordinated regulation of acute-phase genes in general, and the molecular mechanisms of SAA gene expression, in particular. These studies will ultimately contribute to a greater understanding of the biochemical processes leading to amyloid related diseases and lay the foundation for future studies to examine interactions between the inflammatory mediators and their receptors as well as interactions between the intracellular tran-acting factors and the cis-acting regulatory elements.